The present invention relates to a speaker system and a method of controlling a speaker system's directivity and, more particularly, to a system and method of controlling the directivity of a linearly or two-dimensionally arranged speaker system.
Directivity is one of the characteristics used to evaluate the performance of a speaker. Directivity is a property that the magnitude of a sound pressure differs depending on direction. It cannot indiscriminately be said that a wider directivity is better in all applications. There are various directivity patterns for various applications of a speaker, i.e., the range of service of the speaker. For example, for audio use, a wide directivity is preferred, while for loudspeaking applications, a narrow directivity is called for so that voice is radiated only in a predetermined direction to prevent howling, etc.
On the other hand, factors determining the directivity of a speaker include: for a single speaker unit, the structure of a the speaker unit itself, whether it is a cone type or a horn type; and for a cone type speaker, the depth of a cone forming its diaphragm. Further, there is a type of sound that is radiated only in a predetermined direction by a linearly arranged speaker (the so-called "Tonesaulen type") using a plurality of speaker units. At any rate, the directivity of a speaker is determined by the physical structure or arrangement of the speaker unit itself. However, not only does it take time and labor to fabricate a speaker that meets a directivity requirement, but also restrictions are often imposed on the outside dimensions, etc. To overcome this problem, a speaker system that controls its directivity electrically using digital filters has been developed (see Japanese Patent Unexamined Publication No. Hei. 2-239798).
However, the above speaker system is intended to obtain consistent directivity covering a wide range from low to high frequencies, and in the literature there is no indication of any specific control method of obtaining directivity in a desired direction.